Humans have triggered the last 16 record-breaking hot years experienced on Earth since 1937, according to a new study which suggests that without human-induced climate change, recent hot summers and years would not have occurred.
The researchers also found that this effect has been masked until recently in many areas of the world by the wide use of industrial aerosols, which have a cooling effect on temperatures.
"Everywhere we look, the climate change signal for extreme heat events is becoming stronger," said lead author Andrew King, a research fellow at the University of Melbourne.
"Recent record-breaking hot years globally were so much outside natural variability that they were almost impossible without global warming," said King.
The researchers examined weather events that exceeded the range of natural variability and used climate modelling to compare those events to a world without human-induced greenhouse gases.
According to the new study, record-breaking hot years attributable to climate change globally are 1937, 1940, 1941, 1943-44, 1980-1981, 1987-1988, 1990, 1995, 1997-98, 2010 and 2014.
"In Australia, our research shows the last six record-breaking hot years and last three record-breaking hot summers were made more likely by the human influence on the climate," King said.
"We were able to see climate change even more clearly in Australia because of its position in the Southern Hemisphere in the middle of the ocean, far away from the cooling influence of high concentrations of industrial aerosols," he said.
Aerosols in high concentrations reflect more heat into space, thereby cooling temperatures. However, when those aerosols are removed from the atmosphere, warming returns rapidly.
The researchers observed this impact when they looked at five different regions - Central England, Central Europe, the central US, East Asia and Australia.
There were cooling periods, likely caused by aerosols, in Central England, the central US, Central Europe and East Asia during the 1970s before accelerated warming returned, and aerosol concentrations also delayed the emergence of a clear human-caused climate change signal in all regions studied except Australia, according to the study.
The study was published in the journal Geophysical Research Letters.
